This seemed pretty uncontroversial. I've updated the PEP. On Sat, Mar 19, 2016 at 6:52 PM, Guido van Rossum <gu...@python.org> wrote: > Here's another proposal for a change to PEP 484. > > In https://github.com/python/typing/issues/72 there's a long > discussion ending with a reasonable argument to allow @overload in > (non-stub) modules after all. > > This proposal does *not* sneak in a syntax for multi-dispatch -- the > @overload versions are only for the benefit of type checkers while a > single non-@overload implementation must follow that handles all > cases. In fact, I expect that if we ever end up adding multi-dispatch > to the language or library, it will neither replace not compete with > @overload, but the two will most likely be orthogonal to each other, > with @overload aiming at a type checker and some other multi-dispatch > aiming at the interpreter. (The needs of the two cases are just too > different -- e.g. it's hard to imagine multi-dispatch in Python use > type variables.) More details in the issue (that's also where I'd like > to get feedback if possible). > > I want to settle this before 3.5.2 goes out, because it requires a > change to typing.py in the stdlib. Fortunately the change will be > backward compatible (even though this isn't strictly required for a > provisional module). In the original typing module, any use of > @overload outside a stub is an error (it raises as soon as it's used). > In the new proposal, you can decorate a function with @overload, but > any attempt to call such a decorated function raises an error. This > should catch cases early where you forget to provide an > implementation. > > (Reference for provisional modules: https://www.python.org/dev/peps/pep-0411/) > > -- > --Guido van Rossum (python.org/~guido)
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